Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous and solid materials, including, for example, particulate matter. Particulate matter may include unburned carbon particles, such as soot. Particulate matter may be generated during operation of an engine, as fuel is supplied to the engine and is combusted in one or more combustion chambers within the engine. The engine may expel this particulate matter along with other engine exhaust from the one or more combustion chambers through an exhaust line. If this particulate matter is not filtered or otherwise removed from the engine exhaust, these particulates may be vented to the environment. Due to increased attention on the environment, exhaust emission standards have become more stringent. The amount of particulates emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
In order to remove particulate matter from engine exhaust, an exhaust filtration system may be disposed within the exhaust line. The exhaust filtration system may include a particulate filter or trap that may remove particulate matter from the engine exhaust. Particulate filters may typically include a wire mesh medium through which the engine exhaust is passed. The wire mesh medium may filter or trap particulate matter from the engine exhaust. Use of the particulate filter for extended periods of time may cause particulate matter to buildup in the wire mesh medium, thereby causing the functionality of the filter and engine performance to decrease. To avoid this decrease, a heating element may be used to increase the temperature of the trapped particulate matter above the combustion temperature of the trapped particulate matter, thereby burning away the trapped particulate matter and regenerating the filter system. Although regeneration may reduce the buildup of particulate matter in the filter, repeated regeneration of the filter may result in a buildup of ash in the components of the filter over time, or may cause damage to the filter, possibly resulting in a deterioration of filter performance.
At least one system has been developed for diesel particulate filter monitoring. For example, U.S. Pat. No. 6,964,694 to Rauchfuss et al. (“Rauchfuss”) discloses incorporating one or more acoustic sensors into an exhaust system of an engine for detecting one or more frequencies passing through a filter. The one or more acoustic sensors may be fluidly or mechanically coupled to portions of the exhaust system to determine the frequency caused by the exhaust flow through the filter. The acoustic emissions from the filter may be compared to a known filter state to determine the present filter state. However, if the engine in Rauchfuss is not in operation, and no exhaust flow is being produced, then there are no frequencies or sounds for the one or more acoustic sensors to detect. When there are no frequencies or sounds to detect, the system in Rauchfuss cannot readily determine the state and/or loading of the filter.
The present invention is directed to overcoming one or more of the problems set forth above.